An indwelling catheter (e.g., central venous catheter) commonly is placed into a central blood vessel of a patient undergoing medical treatment for prolonged, long-term, or chronic conditions. The catheter provides for infusion of therapeutic materials such as, for example, chemotherapy agents. The presence of an indwelling catheter often increases the risk of deep vein thrombosis (DVT), which is the formation of a blood clot (thrombus) in a deep vein. Although the causes of DVT are not well understood, it may occur as a result of turbulence or other disruption in blood flow caused by the catheter. The blood clot may become dislodged (at which time it is termed an embolus) and move through venous circulation to another location in the body. This is particularly serious if the embolus is transported through venous circulation to, and through, the heart, where it can become lodged with and block a pulmonary artery. This blockage of blood flow to a region of the lungs can cause permanent lung damage or death. If the embolus lodges elsewhere in the body, for example where it impedes or blocks blood flow in a muscle of an extremity, it can cause extreme pain and permanent tissue damage.
In many patient populations, so-called blood-thinners (e.g., warfarin, heparin) are introduced systemically when an indwelling catheter is present in order to decrease the risk of DVT. However, there are significant potential side effects from such treatment including increased risk of bleeding and hemorrhage. These risks may be even greater for patients suffering from conditions where use of an indwelling catheter is indicated.
Pediatric patients are often at risk of DVT in conjunction with an indwelling catheter. However, the risk of DVT in pediatric patients is generally low enough that the risk of side effects from use of blood-thinners outweighs the risk of embolus formation and blood-thinners are not used as commonly as in, for example, geriatric patients. The risk-balancing calculus associated with these facts must also take into account that DVT is considered more serious in pediatric patients because they have the opportunity to live an entire life span of 60-80 years after a pediatric DVT incident, and the damage done by an embolus can have crippling long term effects on development and quality of life. Of course, improved long-term quality of life and reduced risk of DVT is important for patients of any age.
For this reason, it is desirable to provide an indwelling catheter and method of use that may reduce the risk of DVT associated with use of an indwelling catheter. One such approach has used heparin impregnated in polymers of a catheter itself or applied to its surface. This approach is useful, but there may also be a need for adjustable control or user-selectable location-targeting of an anti-DVT agent, which may also be desirable to provide treatment tailored for individual patients based upon age and other specific indications for treatment.